A view of the world from the Wairarapa

Tsunami

July 20, 2009

Those following the hysteria on Twitter just after the big Fiordland earthquake last week might have thought New Zealand had been decimated by a large earthquake and was about to be inundated by a tsunami.

Kiwiblog outlines what the Ministry of Civil Defence and Emergency Management (MCDEM) does in the event of a warning

The MCDEM gets notified of any PTWC warning, plus receives its own data from Geonet.
They then decide what risk, if any there is to NZ. Most of the time
there is none. They will then issue one of three statements:

No tsunami threat to NZ

Potential tsunami threat to NZ

Tsunami warning – threat to NZ

So unless the warning has come from MCDEM,
it is just an automatically generated warning from PTWC. NZ gets around
one of these a month, and none have ever eventuated in the last few
decades.

However there may be times that a tsunami is generated locally. Or
in other words it will hit within 30 to 60 minutes, not hours. If one
is generated locally, then it may hit before an official warning is
possible. These are the warning signs for people in coastal areas:

experience a strong earthquake (it was hard to stand up)

experience a weak earthquake lasting a minute or more

observe strange sea behaviour, such as the sea level suddenly rising and falling

hear the sea making loud and unusual noises or roaring like a jet engine